1. Technical Field
This invention relates generally to a mobile communication system wherein communications are enabled with a mobile station through signposts, and more particularly to a novel TDMA (time division multiple access) mobile communication system in which a plurality of signposts are installed in a predetermined area to relay communication to or from a mobile unit, and the signposts thus installed are connected to each other through a transmission network, which is connected to a fixed network.
2. Description of the Prior Art
A mobile communication system is well known in the art in which a plurality of mobile radio base stations are installed in a predetermined area, and while a mobile station is traveling in a area where a mobile radio base station can communicate with such mobile station (a area hereinafter referred to as "a zone", when applicable), communications are carried out between the mobile radio base station and the mobile station. One example of a mobile communications system is an automobile telephone communication system.
In a conventional automobile telephone communication system, the switching of zones during communication is typically carried out as follows: mobile radio base stations receive radio waves from the mobile station and detect the levels of the signals received, which are sent to a mobile control station; the mobile radio base station whose received signal strength is maximum is then selected.
This will be described in more detail. A mobile radio base station monitors the received signal level of a radio wave transmitted by the mobile station, and, when the signal level goes lower than a predetermined value, transmits a level deterioration signal to a mobile control station. Upon reception of the level deterioration signal, the mobile control station requests the remaining mobile radio base stations around the mobile radio base station in question to monitor the signal levels of that station, and receives monitored signal level data from those mobile radio base stations. In the mobile control station, the monitored level data are compared, so that the mobile radio base station maximum in signal level is newly selected. After a circuit is set up between the mobile radio base station thus newly selected and the automobile switching center, the previous mobile radio base station is instructed to disconnect its channel.